1. Field of the Invention
The present invention relates to a medium supplying unit and an image forming apparatus having the same, and more particularly, to a medium supplying unit and an image forming apparatus having the same capable of reducing the occurrences of concurrent pick up and/or supply of multiple printing media.
2. Description of the Related Art
An image forming apparatus performs a printing operation to form a visible image on a printing medium by means of a developer or an ink based on an image data. To this end, the image forming apparatus includes a medium supplying unit holding and supplying the printing during the printing operation.
A conventional medium supplying unit typically includes a loading plate on which a plurality of printing media are stacked, and a pickup roller for picking up the printing medium an individual sheet at a time. That is, when the printing operation starts, the pickup roller rotates, and picks up and supplies a sheet of printing medium from the top of the stack of the printing media.
However, due to various possible reasons, including, for example, static charges in the sheets of printing media, more than one sheet may concurrently be picked up or otherwise supplied by the pickup roller, which may result in the printing medium being jammed inside the image forming apparatus causing the apparatus malfunction or to be inoperable.
There are various methods heretofore suggested for preventing the problem of multi-sheet supply, and among these, a medium supplying unit employing a cam that rotates in an interlocked manner with the pickup roller, and that by so rotating selectively separates the loading plate from the pick up roller. In these type of medium supplying units, after a printing medium at the top of the stack has been picked up by the pickup roller, the cam rotates into position to push the loading plate away from the pickup roller.
However, because the multi-sheet supply is typically caused by the contact or the attractions between the sheet on the top of the stack with those few sheets immediately below, the movement of the loading plate away from the pick up roller as practiced in the legacy medium supplying unit in-and-of-itself may not be sufficient in reducing the occurrences of the multi-sheet supply.